Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
201 PM EST Sun Mar 06 2022
Valid 12Z Wed Mar 09 2022 - 12Z Sun Mar 13 2022
...Overview...
Broad troughing over the CONUS midweek should be reinforced by a
couple of potent shortwaves, the first diving into the Northwest
Wednesday and another reaching the north-central U.S. Thursday
into Friday. These features should press the trough axis eastward
late week into the weekend, along with an Arctic cold front that
will spread chilly temperatures across the interior West and
central U.S. and into the East by the weekend. Expect snow to the
northwest of the low from the central Rockies/Plains to the
Midwest on Wednesday and Thursday, with less certain potential for
wintry weather over the Ohio Valley and interior Northeast Friday
and Saturday. Meanwhile showers and thunderstorms are likely in
the Southeast through late week before the cold front clears out
the moisture by next Sunday. Flow should become somewhat more
zonal across the CONUS early next week as the trough lifts out of
the East, with weak systems through the northern tier states.
...Guidance Evaluation/Predictability Assessment...
Model guidance continues to show fairly good agreement for the
overall pattern especially initially in the medium range period
given the large scale of the features--strong East Pacific
ridging, troughing across the lower 48, and a subtropical high
over the Caribbean to ridging in the Atlantic. However, there are
some differences in the shortwave details that become impactful by
the latter part of the week especially with the timing of the
trough's movement and thus the cold frontal timing. Broadly, the
GFS model suite is faster with the trough axis and front pressing
eastward compared to the ECMWF suite and the CMC. This is shown by
most individual ensemble members as well as the operational runs
and ensemble means from the 00/06Z cycle, and remained the case in
the 12Z guidance that has come in thus far. Given typical model
performance, the WPC forecast attempted to take an approach in
between but somewhat favoring the ECMWF suite, which slowed the
front and trough axis down from continuity a bit. The 06Z GFS was
somewhat slower and thus better clustered with other guidance
compared to the 00Z run, so preferred the 06Z run. Differences in
the trough/front also lead to variability with the strength and
progression of Great Lakes low pressure Friday and its eventual
track northeastward--overall slower to strengthen and move. As
noted in the previous discussion, CMC runs including yesterday's
12Z and today's 00Z end up closing or almost closing off an upper
low in the Midwest by Saturday, which is an outlier compared to
other guidance that keeps the trough phased with a northern Canada
upper low. Thus the CMC was not preferred, but its new 12Z run
seems comparatively more in line with consensus. Then there is
fairly good model consensus for the ridging initially over the
East Pacific to track inland late week, but then get suppressed by
shortwave energy approaching or entering the Pacific Northwest by
next Sunday, but there are still uncertainties with the timing of
shortwaves and surface features there.
In summary the WPC forecast began with a multi-model deterministic
blend, and gradually transitioned to a blend favoring the ECMWF in
terms of deterministic guidance with some 06Z GFS input, and
adding and increasing the proportion of the ensemble means,
particularly the ECENS mean, to reduce individual model
differences.
...Weather Highlights/Threats...
A stationary boundary settling across the Southeast and ample
moisture and instability from the Gulf of Mexico should keep
showers and storms in the forecast Wednesday to early Saturday.
Localized heavy rainfall rates are likely in this environment, and
flooding/flash flooding may be a threat with heavy downpours,
especially where multiple rounds of convection track over the same
areas during the period, despite the antecedent dry conditions.
Meanwhile, a shortwave moving through the West on Wednesday will
continue a threat for heavy mountain snows for parts of the
interior West and central Rockies. A low pressure system spinning
up in the lee of the Rockies and lifting into the Upper Midwest
Thursday-Friday brings a winter storm threat from the central
Plains to the Upper Midwest. The elongated upper trough should tap
Gulf of Mexico moisture with widespread rain into the East ahead
of the cold front on Friday, with some potential for wintry
weather on the northern/western side of the precipitation shield,
but with low confidence for amounts and placement at this point.
The next system coming into the Northwest next weekend is likely
to increase rain and mountain snow chances across the Pacific
Northwest and northern Rockies.
Arctic sourced air will spill into the Plains, with daytime highs
20-30+ degrees below normal as far south as Texas through Friday.
Overnight lows across the northern Plains and in higher elevations
of the Rockies are likely to be near or below zero for many
locations. Ahead of the cold front, above normal temperatures
should spread across the eastern third of the country Thursday and
Friday before being replaced by below normal temperatures by
Saturday following the passage of the cold front. By next Sunday,
most of the country should modify closer to normal as upper flow
become less amplified, though with lingering cool temperatures in
the East and along the Gulf Coast.
Tate
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml